It is generally known that high-voltage transformers, for example, in a voltage range of from 110 kV or 380 kV and in a power range of 100 MVA or higher, both for inspection purposes and after termination of any possible maintenance or repair work or else directly after their fabrication, need to be tested intensively in order to ensure their correct functioning for the next operation time period, which is often a number of years. Both stationary and mobile testing stations are used. The latter are in particular constructed for in-situ testing of transformers, then dismantled and transported to the next use location. Even when the transport and construction of a mobile testing station is usually associated with a very high degree of complexity, this complexity is usually nevertheless lower than the complexity involved in transporting a transformer with a weight of for example 200 t to a stationary testing station. Advantageously, in addition the downtime of a transformer undergoing testing is then significantly reduced.
In this case, both DC and AC testing stations are used, with which the corresponding test conditions can be produced. In particular, AC testing stations need to be capable of providing a high electrical testing power with variable frequency and variable voltage over a relatively long time period, often lasting several hours, for example for a continuous load test or a short-circuit test. In this case, owing to their high degree of flexibility, rotary converters have proven successful, but they have also proven very maintenance-intensive owing to the mechanical wear. In addition, the transport, construction and dismantling of such a converter is very labor-intensive and additional vibration-damping measures need to be provided for the installation subsurface.
It has therefore proven disadvantageous in the case of existing AC testing station systems that they require a high level of complexity for transport, construction and dismantling and, owing to the rotary converter which is typically used, are also very maintenance-intensive.